After bageling Sorana Cirstea in the first set, Kerber dropped the second, 6-3, and found herself down 5-3, 40-15 in the third on Cirstea's serve. Kerber, though, managed to win that game and the following three for the 60 36 75 victory.

"In the first set I played very well," said the fourth-seeded Kerber. "But in the second set Sorana was playing unbelievably. I was trying to play my game, but nothing seemed to work. I just tried to keep fighting. I'm very happy I won this match and that I'm in the semis tomorrow."

Kerber has now made the final four in five of her last seven events, including her season debut last week in Auckland and the US Open last September. However, she lost each of those semifinals, so will be seeking to change that trend against fellow German Mona Barthel.

A day after her career-best triumph in terms of ranking, Barthel had her third-best in beating 34th-ranked Jarmila Gajdosova, the defending champion. After a slow start in the first set against the No.5 seed, Barthel jumped out to a 3-0 lead in the second and 5-1 in the third en route to a 26 63 62 win, matching her career-best showing - a semifinal appearance in Copenhagen last October. She is looking to become the first qualifier to make a WTA final since Aravane Rezai in Dallas last August.

"I have never played against her before," said Barthel of Kerber. "She's playing really good tennis, really aggressive. I think it's going to be a really good match. I have nothing to lose here. I've already gotten so far. I just want to enjoy it and we'll see what happens."

Friday's other semifinal will see No.1 seed Yanina Wickmayer square off with No.6 seed Shahar Peer. After being knotted at 4-4 in the first set of her quarterfinal against Simona Halep, Wickmayer took the next eight games for a 64 60 triumph. She is the only semifinalist yet to lose a set this week. As for Peer, she was up 46 64 10 on Anna Chakvetadze when the Russian had to retire with a left leg cramp.